Friday, November 16, 2007

Partly cloudy, windy, cold. Persistent winds kept last night's lows from being quite as cold as expected, but temperatures this afternoon have had a hard time maintaining the upper 40s in most of the Washington metro region. By mid afternoon, National was 46°, and Dulles was 44°. The highs were: National 48°, Dulles 46°, BWI 46°. The northwesterly wind gusting frequently over 25 mph has also brought drier air along with the cold; dewpoints are mainly in the low 20s with even a few upper teens. The nearest precipitation on radar consists of some snow flurries over the mountains of western Pennsylvania.

Tonight and Tomorrow

Cold overnight, then increasing clouds and milder. The drier air along with diminishing winds should bring lower lows tonight, near 35° downtown ranging to some upper 20s in 'burbland. A weak "clipper" system diving southeastward from the southern Great Lakes tomorrow will produce increasing clouds and somewhat milder temperatures by tomorrow afternoon with highs 49-53° and a chance of light rain or snow showers late in the day or at night.

For the outlook through the rest of the weekend and towards Thanksgiving, scroll on down to Matt's post below.

Winter Outlooks

Matt reviewed Bob Ryan's winter outlook from last night in his earlier post.

According to an on-air promo, the WUSA-TV, channel 9, outlook will be on the 5pm newscast tonight.

In what may be some kind of a Guinness World Record, 3 out of the 6 front-page articles in today's WaPo involve climate science and related policy:

"Calif. Court Rejects SUV Mileage Rules" (above the fold): "A federal court in California yesterday rejected the Bush administration's new fuel economy standards for light trucks including SUVs, ruling that the government failed to take into account the effects of carbon emissions and their possible link to global warming."

"Katrina, Rita Caused Forestry Disaster": The forest destruction caused by Rita and Katrina "was so massive that researchers say it will add significantly to the global greenhouse gas buildup -- ultimately putting as much carbon from dying vegetation into the air as the rest of the nation's forest takes out in a year of photosynthesis." (According to the article abstract in today's issue of Science Magazine, the storms caused "mortality and severe structural damage to ~320 million large trees totaling 105 teragrams of carbon, representing 50 to 140% of the net annual U.S. forest tree carbon sink.")

"Scientists Fault Climate Exhibit Changes": "Some government scientists have complained that officials at the Smithsonian's National Museum of Natural History took steps to downplay global warming in a 2006 exhibit on the Arctic to avoid a political backlash, according to documents obtained by The Washington Post."

Programming note:PM Update will be off next week. Have a great Thanksgiving, everyone!

Thursday, November 15, 2007

Variable clouds, colder. Following the morning showers, heavy at times, which brought around ¾" of much-needed precipitation to the Washington metro area, some sunshine through scattered to broken clouds has allowed afternoon temperatures to reach at least 50° in most locations. Westerly winds gusting as high as 30 mph have added to the the chilling effect, however. The day's highs occurred in the early morning hours: National 65°(3:54 am), Dulles 63° (2:41 am), BWI 63° (5:48 am), and the lows so far have been right around noon.

Tonight and Tomorrow

Clearing, cold. A lingering shower is possible through early evening, then clouds will decrease overnight with lows 34-39°. Tomorrow will be mostly sunny and breezy with some passing clouds and highs only 46-49°.

For the outlook through the weekend and beyond with Larson's Long-Range, scroll on down to Josh's post below.

Tropical Topics

The Associated Press and AFP covered the landfall of severe Cyclone Sidr, which occurred on the southwestern coast of Bangladesh shortly before noon, Washington time. Preliminary reports indicate that huge evacuations, prompted by early warnings, may have substantially reduced potential casualties.

Wednesday, November 14, 2007

Mostly sunny, mild. After a brief step backward, the seasonal calendar is about to take a jump forward to more wintry temperatures. What happens thereafter is subject to a bit of debate among the models, but the storm development noted in Dan's earlier post has disappeared from the run of the same model made 12 hours later.

By mid afternoon today, however, readings were well into the 60s throughout the area, with Dulles at 68° and National 66°. Salisbury, Culpeper, Leesburg, Manassas and Patuxent River all reached at least 70°. The air is also quite muggy with dewpoints generally in the mid to upper 50s.

Tonight and Tomorrow

Mostly cloudy, showers likely, then turning colder. Skies will become mostly cloudy overnight with showers likely and thunderstorms possible, mainly after midnight and through tomorrow morning. Lows will be 48-53°. Clouds will decrease tomorrow afternoon along with increasingly brisk and gusty northwesterly winds. After morning highs in the low 50s, temperatures will drop during the day to the low 40s by evening.

For the outlook through the rest of the week and into the weekend, scroll on down to Dan's post below.

Prof. Peter Stone of the MIT Center for Global Change Science gave a very interesting presentation last night on the science behind climate change modeling. With the current model inconsistencies over what may or may not develop as soon as early next week, this is an especially relevant time to review the difference between weather and climate modeling. PM Update asked Dr. Stone how he would explain this, and his answer was very similar to what has been said here in the past, but it bears repeating:

Even though climate is the long-term average of the weather, and even though the basic laws of physics apply equally to both problems, climate modeling is not simply taking a weather prediction model and running it for a much longer time. It is much easier, and more accurate, to predict the average conditions produced from the long-term equilibrium of a set of forces than to predict the specific details of the evolution from a beginning state to some point in the future. For the more technically inclined, this is the difference between an initial-value problem (hard) and a boundary-value problem (not so much). Weather prediction is an initial-value problem; it starts from a given set of conditions and predicts the details of their change over time. Climate prediction is a boundary-value problem; it applies a set of forces to a beginning state and predicts the final equilibrium result.

In the course of his lecture, Prof. Stone disclosed some tentative results, now in peer review for future publication, regarding likely future temperature increases. Based on a "business as usual" scenario (no reduction in CO2 emissions), his research indicates that the median prediction of the mean global temperature increase by the end of this century is 4.9°C, with a 90% confidence interval of 3.0-7.7°C. This is sharply higher than the results presented in the latest IPCC report of a range of 2.0°- 4.5°C for a doubling of CO2. To put this into perspective, the predicted increase produces a higher mean temperature than has occurred in the last 3 million years.

Monday, November 12, 2007

Mostly cloudy, cool. After 8 consecutive days at or below average, temperatures in the Washington metro area will warm somewhat for a couple of days before the next cooldown later in the week. Under some sun, but mostly cloudy skies, temperatures this afternoon have remained mostly in the low and mid 50s as a warm front edges northeastward. To the south, Fredericksburg, Culpeper, and Stafford had all reached the 60s by 2pm. Today's official daily highs and rainfall totals are: National 54°/0.24", Dulles 58°/0.24", BWI 54°/0.18".

Mostly cloudy, milder. Lows tonight under mostly cloudy skies will be in the mid to upper 40s; some scattered showers are possible. Tomorrow will be mostly cloudy with a 30% chance of showers and highs 62-66°.

For the outlook through the rest of the week and into the weekend, scroll on down to Jason's post below.

Science and Service

This Veterans Day in the 200th anniversary year of its direct predecessor's founding is an appropriate time to salute the men and women of the "Seventh Service" who serve the nation through science. See the Veterans Day 2005 PM Update for more information. (For what it's worth, one of the links has moved; the Portrait of an Updater as a Young Man is now here).

Climate Seminar Series

At last report, the MIT Club seminar series, "The Great Climate Change Debate" still had a few seats left for the 5 remaining monthly dinner lectures at a pro-rated cost. PM Update will pay the cost for the first TV meteorologist who agrees to attend all sessions and report on the contents on air in prime time. If you're interested, however, you need to act fast---the next meeting is Tuesday night.

Great Climate Hoax

John Coleman's assertion of hoaxiness in the climate change debate, extensively discussed in Andrew's Undercast and comments yesterday, is not the only climate issue bouncing around the blogosphere in recent days. A paper in the Journal of Geoclimatic Studies claiming that CO2 increases are primarily caused by deep-sea bacteria has also attracted a lot of attention. Before you jump on the bandwagon, however, you might want to see what Nature.com and last night's post by the NYTi's Andrew Revkin had to say on the subject.